G. MASSEE OX BASIDIOMYCETES. 3 



before tliey are capable of germination ; thus tiding the fungus 

 over that period of the year unsuited for its active growth, 

 germinating during the spring following their formation, at the 

 time when the host-plant has appeared, when inoculation takes 

 place, and the cycle of development of the fungus commences 

 anew, with the formation of the conidial stage. 



The conidial condition of numerous fungi are popularly known 

 as mildews, moulds, rusts, etc. ; and the point of greatest im- 

 portance to remember is the fact that these conidial forms, by 

 gradual differentiation, gave origin to the enormous assemblage 

 of fungi known as the Basidiomycetes ; the older sexual form of 

 reproduction being entirely suppressed. 



The enormous assemblage included in the Basidiomycetes, 

 numbering about eleven thousand species, and embracing almost 

 every conceivable range in size, form, colour, and texture — from 

 the minute cobweb-like structure of some species of Cm'ticium^ 

 to the gigantic pufif-ball, often more than a foot in diameter, and 

 the complex structure of the gill-bearing agarics — all betray a 

 common origin in retaining the exact type of spore-bearing 

 structure, called basidia, present in the most primitive types of 

 the group. These basidia are simply the swollen tips of ordinary 

 hyphse or branches of mycelium, and are club-shaped ; the free, 

 rounded end of each basidium usually bears four slender spines 

 or sterigmata, each sterigma in turn producing a spore at its tip. 

 The basidia are packed in immense numbers side by side, forming 

 a continuous surface called the hymenium, which in course of 

 time becomes covered with spores borne by the sterigmata 

 springing from the swollen tips of the basidia, which collectively 

 form the surface of the hymenium. The surface of the gill of an. 

 agaric is covered with a structure of this kind, and the gradual 

 change of colour observed in the gills of some agarics — as in the 

 common mushroom, where the change is from white, through 

 pink, to dark brown — is due to the gradual ripening of the spores. 

 All spores are colourless at first, and in some groups remain per- 

 manently so ; in other groups the wall of the spore gradually 

 changes colour, until at maturity it is salmon-colour, rust-colour, 

 purple, or black, depending on the particular species. 



In briefly tracing the evolution of one section of the Basidio- 

 mycetes, called Hymenomycetes, characterised by having the 

 hymenium exposed from the earliest period of its formation,. 



